1. Field of Invention
The invention relates to an ink jet printer that ejects ink from a print head to form an image on a recording medium, and, more particularly, to a serial-type ink jet printer that forms the image by supplying the ink through a tube to the print head reciprocating in a width direction of the recording medium.
2. Description of Related Art
Some conventional ink jet printers are separately provided with an ink container that contains ink and a print head. The ink is supplied to the print head from the ink container through a tube. Such structure enables the print head to be reduced in size, as compared to a structure where the print head is integrally provided with the ink container. If a serial-type ink jet printer employs separate structures for the print head and the ink container, the size and weight of the print head is reduced and consequently loads to a carriage motor is reduced. Accordingly, the downsized carriage motor can be used.
When the ink is supplied to the print head from the ink container through the tube, as described above, the tube may be provided to the print head so as to protrude from a top surface of the print head (surface opposite to a platen), or so as to protrude from surfaces of the print head on each end side in a moving direction thereof. The latter structure is desirable, especially when the ink jet printer needs to be low-profile and compact as a mobile printer.
In this case where the tube is protruded from a surface of the print head on an end side in the moving direction thereof, the tube bends as the print head moves. A roller that transports a recording medium to a direction (sub scanning direction) perpendicular to the moving direction of the print head (main scanning direction) may often be disposed near the platen, that is, near a moving area of the print head. The roller is preferably disposed near the print head to prevent the recording medium from floating or lifting.
With such a structure as described above, the flexing tube is likely to make contact with the roller. When the tube contacts the roller, the tube is caught on a frictional member (such as rubber and coating) provided on a surface of the roller, so that a resistance may be applied to the print head during its movement or the tube may be damaged by the roller rubbing the surface of the tube. Accordingly, the resistance to the movement of the print head causes a change in a moving speed of the print head, so that positions where ink is to be ejected cannot be precisely controlled. The tube caught on the roller might have damages that result in an ink leakage from the tube.
To prevent the roller and the tube from making contact with each other, the roller may be covered partially at least on the side near the tube. However, when the flexing tube makes contact with the cover, the tube is raised and may result in resistance to the movement of the print head. In addition, an encoder strip, as a position identification member, may be provided near the moving area of the print head along the moving direction of the print head, so that the range where the tube is allowed to bend may be restricted. If some special devices are provided to restrict the bending of the tube, the downsizing of the ink jet printer becomes difficult.
Accordingly, one aspect of the invention is to provide an ink jet printer that forms an image by supplying ink through a tube to a print head reciprocating in a width direction of a recording medium, wherein bending of the tube is restricted without providing a special device for the ink jet printer and without applying a significant resistance to the movement of the print head.
To achieve the aspect of the invention an ink jet printer according to the invention may include a print head that forms an image onto a recording medium by ejecting ink, an ink container that contains the ink supplied to the print head and is provided separately from the print head, a guide rail that guides the print head in a width direction of the recording medium, a print head moving device that reciprocates the print head along the guide rail, a tube member that protrudes from a surface of the print head on an end side in a moving direction thereof, connects the print head and the ink container over a full range of a print head moving area to supply the ink from the ink container to the print head, and has elasticity, a roller that feeds the recording medium in a direction perpendicular to the guide rail and is disposed near the guide rail, and a cover that covers the roller to prevent the tube member, that bends as the print head moves, from contacting the roller. The cover and the guide rail may be disposed along a plane substantially vertical to a direction that the tube member bends as the print head moves. The cover and the guide rail may be disposed with a distance therebetween that prevents the tube member from passing through the distance between the cover and the guide rail.
In the ink jet printer according to the invention, a face of each of the guide rails that guides the print head in the width direction of the recording medium and the cover that prevents the tube member from contacting the roller may be disposed on a plane substantially vertical to a direction that the tube member bends. In addition, the cover and the guide rail may be disposed with a distance therebetween that prevents the tube member from passing through the distance between the cover and the guide rail. The cover and the guide rail may constitute such a vertical plane that blocks the bending of the tube member.
According to the invention, the tube member may be prevented from bending beyond the guide rail and the cover, without providing special devices for the ink jet printer. Therefore, if the position identification member is provided on a side opposite to the print head with respect to the guide rail, the position identification member may be prevented from being contaminated as the tube member makes contact with the position identification member. Further, the guide rail and the cover may constitute the plane substantially vertical to the direction in which the tube member bends. Therefore, when the bending or the movement of the tube member is blocked by the guide rail and the cover forming the plane vertical to the direction that the tube member bends, the tube member may not be raised. When the bend in the tube member dynamically flexes as the print head reciprocates along the guide rail, a volume trajectory delineated by the dynamically flexing bend is substantially contained within a volume of a trajectory delineated by the print head while the print head reciprocates. Consequently, resistance to the movement of the print head may be minimized. Therefore, ink ejection positions may be precisely controlled.
Further, the tube member that supplies the ink from the ink container to the print head may be set with a flat cable that supplies current to the print head, and may be moved together with the flat cable. The tube member and the flat cable may be tied in a bundle by a tying member of a coupling member (tube band). The distance between the cover and the guide rail may be shorter than a length of the tying member, so that the tube member or the flat cable may not pass through the distance between the cover and the guide rail.
With the above-described structure, the distance between the cover and the guide rail may be narrower than the length of the tying member that holds the tube member and the flat cable in a bundle. Therefore, as described above, the tube member may be prevented from bending beyond the guide rail and the cover. The bending of the tube member may be restricted by making the tying member contact with the cover and the guide rail. Therefore, the distance between the cover and the guide rail, and a dimension of a tube constituting the tube member, as well as a width of the flat cable may be freely set, increasing design flexibility.
Preferably, a plurality of the tubes constituting the tube member may be divided into two tube groups. Each tube group may be protruded from one surface of the print head on an end side in a moving direction of the print head. The flat cable that supplies the current to the print head may be set with each tube group protruding from one surface of the print head.
The tubes supplying the ink therethrough from the ink container provided separately from the print head may be protruded from the surface of the print head on both end sides in the moving direction of the print head, and may be set with the flat cables that supply the current to the print head. Thus, widths of the tube member and the flat cable may be reduced to half, so that demands for a mobile printer, such as compactness and thinness may be satisfied.
The flat cables may be separated into two, and the separated flat cables may be disposed away from each other. Therefore, crosstalk between the separated flat cables does not occur. In addition, patterns divided into two may be provided for each of the flat cables, so that occurrences of crosstalk may be reduced. Further, each of the flat cables may be set with the tubes and the movement of the flat cables may be stabilized.